The present invention relates to a device for engaging a movable object at one position and advancing it to another position and more particularly relates to a transfer slide assembly employed in a rail conveyor system for transferring a trolley from a rail in a subsidiary system onto an elevator for movement upwardly to a main rail system.
U.S. Pat. No. 4,615,273 discloses a conveyorized transport system of the type embodying the transfer slide assembly of the present invention having a main rail upon which trolleys ride, subsidiary loops located along the main rail leading to and from a work station, and switching means for transferring a trolley between the main rail and each subsidiary loop. It is known to utilize an elevator having a slotted track section which receives a trolley crown portion to lift the trolley from a position adjacent the lower free end of an inclined subsidiary loop rail upwardly toward the switching means for transfer onto the main rail of the conveyor. While the elevator car is sized and shaped to receive the crown portion of the troley, the trolley must be actively and positively pushed or pulled into the elevator car because a trolley travelling down the inclined subsidiary loop rail towards the elevator usually cannot consistently travel from the rail into and through the narrow confines of the elevator car slotted track under the force of its own momentum. In addition, the forward movement of a trolley rolling down off of the inclined subsidiary loop rail end may often be arrested or be significantly reduced by the trolley crown portion entering into the elevator slotted track. Moreover, trolley side sway occurring as the trolley rolls down the rail may further prohibit the crown portion of the trolley from aligning with the elevator car slotted track and thus hinder the trolley from the entering the elevator car.
One type of device previously used to advance a trolley with positive force employs a piston and cylinder assembly such as the one suggested in U.S. Pat. No. 4,615,273 utilizing a hinged claw fixed to a piston rod for gripping a single trolley and pulling it into the slotted track of the elevator. One problem experienced in these previously known advancing mechanisms is the relatively complex mechanical structure of the hinged claw. Since the claw must operate to consistently engage and move successive numbers of trolleys into the slotted track of the elevator, the hinge and the other cooperating mechanical components may become worn and eventually breakdown. In addition, such hinged claw devices tend not to be self-contained compact mechanisms but instead usually involve awkwardly oriented grasping means such as the hinged claw depending from the laterally extending piston rod.
As previously mentioned, a trolley may tend to swing laterally relative to the longitudinal extent of the rail as it approaches the elevator car. This lateral swinging movement may at times prevent an advancing assembly such as the hinged claw from contacting and gripping th trolley crown portion and moving it into the elevator. Moreover, a trolley advancing device such as suggested in U.S. Pat. No. 4,615,273 engages the trolley crown which is positioned on the top portion of a trolley and thereby advances the trolley into the elevator by pulling the trolley from the top. As a result, a yet further problem of tilting about the trolley roller axes occurs when the trolley carries a substantially heavy garment piece and is pulled from its top crown portion by an advancing device. Tilting motion of this type may cause the crown portion of the trolley to become dislodged from the advancing device and in turn may subsequently cause the trolley not to be advanced into the slotted track of the elevator car.
Accordingly, it is the object of the present invention to provide a transfer slide assembly supported at the end of the subsidiary loop rail and positioned adjacent an elevator in a conveyorized transport system having means for positively engaging with a trolley and moving successive ones of such trolleys consistently into the elevator for movement upwardly to a main conveyor rail system.
It is yet another object of the present invention to provide a compact and mechanically simplified transfer slide assembly usable in a conveyorized transport system having generally a two-piece construction such that one piece is fixed to the rail while second piece slides relative to the first to positively push the trolley onto an elevator.
A further object of the present invention is to provide a transfer slide assembly having a dual action stroke capable of advancing a trolley into registry within a slotted track serving as an elevator car.